Barometer



I. E. M CABE Nov. 14, 1950 BAROMETER 3 Sheets-Sheet 1 Filed July 9, 1945 llllll I III] ll l FIG. 1

INVENTOR. IRA E. MCCABE ATTORNEY Nov. 14, 1950 l. E. M CABE BAROMETER Filed July 9, 1945 3 Sheets-SheetZ FIG. 6.

44 h 4 f L 3 Mllllllllllllllllllllll]IIIIIHIIIIWIIlllIlllIllII||||H||IIIIIIIIIIIIIIIIIIIM U FIG].

INVENTOR.

IRA E. MCCABE ATTORNEY Nov. 14, 1950 1. E. M CABE 2,530,063

BAROMETER Filed July 9, 1945 3 Sheets-Sheet 3 m; mums: Q

FIG. IO. A

INVENTOR.

IRA E. MCABE ATTORNEY Patented Nov. 14, 1950 UNITED STATES PATENT FFICE 19 Claims.

The present invention relates generally to instruments for measuring pressure and is more particularly directed to barometers of the elastic ype.

It is recognized that a membrane of an elastic substance secured at the edges will be deformed if the pressure on one side exceeds that on the other. This is the principle underlying the operation of the elastic barometer wherein elastic deformation of some solid system is magnified by a lever arrangement and utilized as an indicator of atmospheric pressure.

There are two main types of elastic barometers, namely, the Bourdon and the aneroid. The Bourdon barometer comprises a curved tube of elliptical cross section, partly or fully evacuated. Changes in atmospheric pressure effect changes in the radius of tube curvature. One end of the tube being fixed, the motion of the free end in response to atmospheric pressure variations is amplified by a system of levers to indicate the extent of the pressure.

Fundamentally, the aneroid barometer consists of an enclosed chamber of thin metal, partly or fully evacuated. When constructed of very thin material, spring means are employed toprevent the chamber from collapsing under the external pressure of the atmosphere. At a predetermined pressure, equilibrium will be established between the force of air and the spring. In practice, the chamber is usually made thin and flexible so that the elastic properties of the spring determine those of the entire instrument. Aneroids, however, when formed and made of heavier materials of suflicient strength require no spring loading and may constitute the available commercial forms, contemplated for use in the structures hereinafter described.

In elastic barometers heretofore known, a number of factors contribute to impair the accuracy and sensitivity of the instruments, such as lag, mechanical hysteresis, friction and lost motion in the moving parts, and elastic errors due to changes in ambient temperature.

Accordingly, it is the primary object of this invention to provide an elastic barometer of the Bourdon or aneroid type characterized by a high order of accuracy and. sensitivity. It is also an object of this invention to provide a barometer of the above type wherein lost motion and friction in the moving parts are eliminated. An additiona1 object of this invention is to providea barometer of the above type which is of simple, rugged and compact construction.

Broadly stated, the objects of this invention are fulfilledby a cooperative arrangement .between an .atmospherically sensitive, elastic element and a cross-spring pivot structure, said arrangement acting in-a manner whereby the move- .as well as other objects and features thereof, reference is made to the following detailed description to be read in connection with the accom- A panying drawing wherein:

Figure 1 illustrates in plan view a preferred embodiment of a Bourdon type barometer in accordance with the invention;

Figure 2 is aside view taken in the direction'of AA of Figure 1;

Figure 3 shows the barometer of Figure 1 as it appears when expanded under low atmospheric pressure;

Figure 4 is,a detail of the cross-spring pivot of Figure 1;

Figure 5 is a fragmentary view of the scale employed in the'barometer of Figure 1;

Figure 6 is a preferred embodiment, illustrated in plan view, of a second Bourdon type barometer in accordance with the invention;

Figure '7 is an end view taken along the line BB of Figure 6;

Figure 8 is a third preferred embodiment of an aneroid barometer in accordance with the invention;

,Figure 9 is anend view taken along the line and expanded.

Referring now to the drawings and more particularly to Figures 1, 2, and 3, wherein like components are designated by likenumerals, thereis shown a barometer comprising a pair of arcuateshaped Bourdon tubes I and II, mechanically coupled to a cross-spring pivot I2, adapted to rotate a mirror I3 mounted thereon, a barometric scale I4, a light source I5 to illuminate said scale and a viewing telescope IB trained on said mirror whereby the angular position of the mirror with respect to the scale furnishes a magnified pressure reading. The instrument is housed within a suitable casing indicated by dashed line H, with the eye-piece of telescope I6 extending without said casing.

Bourdon tubes I0 and II are each secured at one end to a cylindrical post I8 mounted on a rectangular block I9. Means are provided for shifting the position of block I9, said means including a setscrew 20. Bourdon tubes Ill and II are evacuated through a nozzle 2| communicating with both tubes within post I8.

The cross-spring pivot I2 is a form of elastic "hinge comprising a system of four identical pairs of fiat springs 22 connecting three generally 'square frames 23, 24, and 25, the end frames 23 and being supported in the condition of equilibrium by the said pairs of springs 22 at equi- Jspaced and corresponding parallel positions with respect to center frame 24. The springs of each pair '22 are arranged in spaced relation to intersect as in the letter X, and they serve to connect the center frame 24 with the end frames 23 and 25, the springs being fastened at the opposite end portions of the vertical arms of the frames, as may be seen most clearly in Figure 2.

The center frame 2 3 may be separately viewed in Figure 4 and it will be seen that a transverse piece 26 is connected between the horizontal arms of the frame at the midpoints thereof and supports mirror I3 in a central position perpendicular to the plane of the frame. A segment of the front vertical arm of center frame 24 is removed to fully expose the face of mirror I3 to the view of telescope I6.

Bourdon tube II] is linked to pivot I2 by means of a suitably shaped rigid wire 27 affixed atone end to the midpoint of the lower horizontal arm of-frame 25 and at the other end to a lug 28 attached to a free end of tube ID. Likewise, Bourdon tube II is linked to pivot I2 by means of a suitably shaped rigid wire 29 affixed at one -end to the midpoint of the upper horizontal arm of frame 23 and at the other end to a lug 30 attached to the free end of tube I I.

The characteristic of the cross-spring pivot I2 is such that the center frame 24 rotates about the i y mirror I3.

The pivot system is perfectly elastic since there are no moving parts in contact to produce friction; also its construction enables it to withstand a sudden reversal of load which might unseat other types of pivots. Moreover, since there are no moving parts in frictional contact, lag is minimized, no lubrication is necessary and no wear takes place. The barometer components are preferably fabricated of metal having a substantially zero temperature coefficient so that no error will be introduced by reason of thermal changes.

The scale I4 is vertically attached to an adjustable base 3| having an arcuate slot 32 formed therein permitting adjustment of the scale position within the limits defined by the slot. Although scale I4 is of relatively short length, the markings inscribed thereon, as depicted in Figure 5, are designed to enable a wide range of millibar graduations. Scale I4 is formed by evenly spaced vertical lines 33, indicating progressive steps of ten millibar intervals, which are connected by diagonal lines 34, each diagonal connecting two adjacent vertical lines at opposite extremes thereof. Diagonal lines 34 are divided by eleven evenly spaced horizontal lines 35, into ten equal parts, each of the eleven horizontal lines at the point of intersection with a diagonal line 34 registering one millibar. Thus a scale of short length provides a wide range of graduation without crowding of indicia. This scale design is especially useful for barometers of compact construction.

In viewing the reflection of the scale I4 through telescope It, the telescope hairline sight; when "aligned either with a particular intersection of a horizontal line 35 and a diagonal line 34 or a particular vertical line 33, will at that time register the millibar reading for thepressure being recorded.

It will be seen, therefore, that the combination of cross-spring pivot I2 and mirror I3 behaves as a balanced amplifier for the movements of Bourdon tubes It and l I in that a slight displacement of the mirror effects a relatively large shift in the position of the telescope hairline with respect to scale I4.

The calibration of the instrument is accomplished against a standard guage by orienting the scale I4 and block'l9 to a position whereby the scale readings correspond with that of the standard.

Referring now to Figure 6 there is shown in plan view another preferred embodiment of a Bourdon type barometer in accordance with the invention, andto Figure 7 there is shown said barometer in end View as seen along the line B-B inFigure 6. The instrumentv comprises a single Bourdon tube 36 mounted at its midpoint and having both free ends mechanically coupled to respective end frames 3! and 38 of a cross-spring pivot 39. The cross-spring pivot 39 is identical with the pivot l2 discussed in connection with Figure 1 except for the center frame 40 which is adapted to support an indicator 4! comprising two parallel supporting bars 42 attached to the center frame 45, said bars supporting at one end a pointer 43 which rides along an arcuate barometric scale 44. Pointer 43 is counterbalanced at the other end of supporting arms 42 by a weight 45 which serves to maintain proper balance and stability.

, Referring now to Figure 8 there is shown in plan view another preferred embodiment of my invention in. the form of an aneroid barometer, and to-Figure 9 showing said barometer in end view as seen along the line CC in Figure 8. The instrument comprises a pair of evacuated aneroid chambersj 46 and 41, mechanically coupled to a cross-spring pivot 48, rotating a mirror 49 mounted thereon. As in the instrument dis closed' in Figure l, the aneroid barometer includes a scale and a viewing telescope operating in conjunction with mirror 49, but since these :components have already been shown in connection with Figure 1, they are not again reproduced. The cross-spring pivot 48 is identical with the pivot l2 disclosed in Figure 1 except that the mirror 49 is secured below the center frame 50 .coplanar therewith thereby clearing the mirror 'face of all obstructions.

The aneroid chambers 46 and 41 are maintained in parallel relation,

each being bolted on one side to a suitable supporting frame. The free side of aneroid chamber 46 is linked to the end frame 5| by a rigid wire 52, while the free side of aneroid chamber 41 is similarly linked to. end frame 53 by supporting wire "54. The concurrent expansion or contraction of aneroid chambers 46 and 41 in response .to atmospheric pressure causes a lateral displacement of end frames 5| and 53 of the pivot resulting in rotation of mirror 49. Rotation of mirror 49 provides a barometric reading in the same manner as described in connection with Figure 1.

and 59, respectively. Coupled, by means of the screws to mounting pins BI and 62 concentrically attached to their respective aneroids 58 and 59, is a cross spring pivot structure 63, which sustains and actuates a movable electrical contact member 64. At the base of the U bracket 51 a commutator block 65 is secured and provided with a series of contacts whereby the same, when incorporated into the electrical circuit of a radio transmitting system, with the contact member 64, provides a means of registering changes in altitude as expansion and contraction of the aneroids move the contact member over the contacts of the commutator block 55.

The cross spring structure as shown in Figures 10 and 11, when in the state of equilibrium, maintains a pair of base plates 66 and 6'! in parallel relation with a pivot plate 68, the facing surfaces of the said base plates and the pivot plate serving as supports for connecting thereto the ends of the cross springs l2, l3, l5, l6.

Pivot plate 68 serves as a common support for all the spring ends terminating on one side of the cross spring arrangement and also as a support for the movable electrical contact member 64. The two base plates 65 and 61 are movable, independently of each other, and are connected to their respective aneroid chambers 58, 59, to be moved thereby, by angular extensions 69 and HI. The base plates 66 and 61 serve as supports for the other ends of the cross springs.

As may be seen in Figure 11, base plate 61, connected to the aneroid chamber 59, is adapted for movement through a cutout portion H at the center of base plate 66. The spring structure connecting the base plate 61 to the pivot plate 68 comprises two spaced-apart springs 12 centrally located between two springs 13, the inner springs 12, arranged in relation to the outer springs 13, to provide an intersection as at 14, like the letter X, as shown in Figure 10.

Asmay be seen inFigures 10,. and 11, base plate 66, attachedrto aneroid chamber .58 .isltie'd to the pivot plate 68 by two pairs .of-springs I5 and 16, each pair 1 arranged in theform of-..the letter X and located, one pair oneach side .0 the opening H.

As heretofore mentioned, *the pivot plate 68 also servesas a support. for .the'movable contact member 64. As viewed in Figure 10, a right angle extension 11 provides a means to connect, by a cross spring pivot structure 18 identical with that formed by springs 12 and 13, the base 68 and contact member 64 to provide a resilient and flexible juncture.

To compensate for variations in expansion between different sets of aneroid chambers, over the same pressure change range, the connecting extension 10 to aneroid chamber 59 may be pro- .vided with an arcuate slot through which the screw 60 may secure the extension to the aneroid. By shifting the base plate 61 so that the intersection 14 is moved closer to, or further from, intersection 19, according to the amount of expansion provided by the aneroid chambers, adjustment can be made to provide sufficient movement of the movablecontact 64 over the. full scale with the available movement of the aneroids.

Referring to Figure 10, the free extremities of the U bracket 5'! are joined together by a connecting rod 80. The rod is threaded at each end, one of the threads being of smaller diameter and finer than the other. .The ends of the bracket are threaded to receive on one side the coarse-threaded end of the rod and the other the fine-threaded end. Upon proper assembly the rod may be turned to widen or narrow the distance. between the aneroids and thereby. cause movement of the contact 64 to establish the zero or starting contact point fora predetermined pressure condition.

Referring to Figures 12A to D there is shown in detail, the position of the movable contact 64 when the aneroid is contracted and expanded. Figures 12A and B show the amount of movement necessary to cover the scale with the extension 10 bolted to the aneroid 59 as shown in Figure 10, Figure 12A illustrating the condition with a contracted aneroid and Figure 12B with an expanded aneroid. Figures and D show the smaller amount of movement needed of the aneroids to cover the scale, when the base plate 61 is shifted upwardly and bolted to the aneroid 59 at the bottom of the slot, Figure 120 illustrating the condition with a contracted aneroid and Figure 12D with an expanded aneroid.

Thus, there has been shown in several preferred embodiments elastic barometers wherein the movement of the sensitive element or elements is amplified without the use of gears or other moving components introducing lost motion, backlash, friction or other mechanical defects inherent in instruments of the prior art.

While there have been described what are at present considered preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifica tions may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

The combination in an elastic barometer comprising atmospherically sensitive elastic means; of across-spring pivot including three relative to each other; means for imparting the movementof said elastic means to at least one of said lastmentioned two frames; and means re- Isponsive to the rotation of said pivotable fram .to obtain a barometric scale reading.

.frames and cross-springs connecting said pivot Lframe to-each of said base frames; means coupling thefree ends of said Bourdon tubes to said base frames respectively whereby they cooperate :to. rotate said'pivot frame; and means responsive lto'the'rotation of said pivot frame to obtain'a barometric scale reading.

3. The combination in an elastic barometer comprising a pair of Bourdon tubes, both affixed atone? end; a cross-spring pivot structure, said structure including a pivot frame, two base frames and cross-springs connecting said pivot lframeto each of said base frames; means coupling the free ends of said Bourdon tubes to said base frames respectively whereby they cooperate to rotate said pivot frame; a barometric scale; and apointer mounted on said pivot frame as to berotated along said scale.

4. The combination in an elastic barometer comprising a pair of Bourdon tubes, both affixed atone end; a cross-spring pivot structure, said structure including a pivot frame, two base frames and cross-springs connecting said pivot frame to each of said base frames; means coupling the'free ends of said "Bourdon tubes to said base frames respectively whereby they cooperate to rotate said pivot frame; a mirror mounted on saidlpivot frame so as to rotate therewith; a telescope, having a hairline sight, trained on said mirror; a barometric scale having 'graduations so disposed with respect to said mirror as to be viewed in said telescope, whereby the scale graduation coinciding with said hairline provides a scale reading.

1 5. The combination in an elastic barometer comprising a pair ofBourdon tubes, both affixed at one end ;"a cross-spring pivot including a gen-- erally rectangular center frame, a pair of generally rectangular end frames disposed at opposite sides of said center frame, four pairs of flat springs, each pair arranged in spaced relation to intersect as in the'letter X and connecting respectively said end frames with said center frame at the upper andlower portions of the vertical armsthereof; means rigidly'linking the free ends of said Bourdon tubes to said end frames as to laterally displace said end frames in opposite directions in accordance with the movement of said tubes; and means responsive to the rotation of said center frame to obtain a barometric scale reading. 1

6. The combination' in an elastic barometer comprising a pair ofyBourdon tubes, both affixed at one end; a cross-spring pivot including agenerally rectangular center frame, a pair of generally rectangular end frames disposed at opposite sides of said center frame, four pairs of flat springs, each pair arranged in spaced relation to intersect as in the letter X, and connecting respectively said end frames with said center frame at the upper and lower portions of the vertical arms thereof; means rigidly linking the free ends of said Bourdon tubes .to said end frames so as to laterally displace said end frames in opposite directions in accordance with the movement of said Bourdon tubes; a mirror mounted on said center frame to rotate therewith; a telescope,

having hairline sight, trained on said mirror;

a barometric scale so disposed with respect to said mirror as to be viewed in said telescope whereby the scale. marking coinciding with said hairline provides a scale reading; and means to illuminate said scale.

7. The combination in a cross-spring pivot comprising a generally rectangular center frame; a pair of generally rectangular end frames disposed at opposite sides of said center frame; and four pairs of flat springs, each pair arranged in spaced relation to intersect as in the letter X and connecting respectively said end frames with said center frame at the upper and lower portions of the vertical arms thereof, whereby lateral displacement of said end frames in opposite directions causes rotation of said center frame.

8. The combination in an elastic barometer comprising a Bourdon tube affixed intermediate its ends; a cross-spring pivot structure, said structure including a pivot frame, two base frames and cross-springs connecting said pivot frame to eachof said, base frames; means coupling the free ends of said Bourdon tube to said base frames respectively whereby they cooperate to rotate said pivot frame; and means responsive to the rotation of said pivot frame to obtain a barometric scale reading. j

9. The combination in an elastic barometer comprising a pair of aneroid cells; a cross-spring pivot structure includin a pivot frame and two sets of cross-springs connecting said frame to said cells respectively whereby they cooperate to rotate said pivot frame, and means responsive to the rotation of said pivot frame to obtain a barometric scale reading.

10. The combination in an elastic barometer comprising atmospherically sensitive elastic means; of a cross-spring pivot structure comprising a pivotable' member and two relatively movable members coupled respectively to said pivotable member by two pairs of cross springs and also'coupled to said elastic means whereby they cooperate to rotate said pivotable member, and means responsive to th rotation of said 'pivotable member to obtain a barometric scale reading. v I

11. The combination in an elastic barometer comprising atmospherically sensitiv means"; a cross-spring pivot structure comprising relatively movable members coupled to said elasticmeans, a pivot member and cross-springs between said pivot member and each of said movable members whereby operation of said means causes rotation of said pivot member, indicating means responsive to the rotation of said pivot member to obtain a barometric scale readin and me'ansto adjust the coupling between at least one of said movable members and said atmospherically sensitive means to vary the amplitude of movement of the indicating means in accordance with the movement obtainablefrom said sensitive means.

12. The combination in an elastic barometer comprising a pair of aneroid cells; across-spring pivot structure including a pivot member and two sets of cross-springs respectively coupling said member to said cells whereby they cooperate to rotate said pivot member, a commutator'including a'series of electrical conductors, a, movable contact, and means responsive to the rotation of said pivot member to move the contact over the conductors in engagement therewith.

13. The combination in an elastic barometer comprising a pair of aneroid cells; a cross-spring pivot structure including a pivot member, two relatively movable members and two sets of crosssprings connecting said pivot member to said movable members respectively, said relatively movable members respectively being coupled to said cells whereby they cooperate to rotate said pivot member, a commutator including a series of electrical conductors, a movable contact, and means responsive to the rotation of said pivot member to move the contact over the conductors in engagement therewith.

14. The combination in an elastic barometer comprising a pair of aneroid cells; a, first crossspring pivot structure including a pivot member, two relatively movable members and first and second sets of cross-springs connecting said pivot member to said movable members respectively, said relatively movable members respectively being coupled to said cells, whereby they cooperate to rotate said pivot member, a commutator including a series of electrical conductors, a movable contact and a third set of cross-springs coupling said pivot member to said contact, whereby rotation of the pivot member moves the contact over the conductors in engagement therewith.

15. The structure of claim 13 wherein means are provided for adjusting the relative positions of said movable members, to vary the amplitude of movement of the contact, in accordance with the movement obtainable from the cells.

16. The structure of claim 14 wherein means are provided for adjusting the relative positions of said movable members, to vary the amplitude of movement of the contact, in accordance with the movement obtainable from the cells.

17. The combination in an elastic barometer comprising a pair of aneroid cells; a U bracket supporting one of said cells upon the inner face of each leg adjacent the free ends thereof, a commutator adjacent the opposite end thereof including a series of electrical conductors, a crossspring pivot structure including a pivot member, two relatively movable members and first and second sets of cross-springs connecting said pivot member to said movable members respectively, said relatively movable members being coupled to said cells whereby they cooperate to rotate said pivot member, a, movable contact, a third set of cross-springs, coupling said pivot member to said contact, whereby rotation of the pivot member moves the contact over the conductors in engagement therewith and means for adjusting the free ends of the bracket relative to each other to adjust the contact to its initial position.

18. The structure of claim 17 wherein means are provided for adjusting the relative positions of said movable members, to vary the amplitude of movement of the contact, in accordance with the movement obtainable from the cells.

9. In a barometer, the combination of a cross spring pivot structure, the said pivot structure including a pivot frame member, first and second auxiliary frame members spaced from said pivot frame member, a first pair of crossed springs joining the pivot frame member to the first auxiliary frame member, and a second pair of crossed springs joining the pivot frame member to the second auxiliary frame member, whereby said pivot frame member is rotated upon movements of the auxiliary frame members relative to each other; and pressure-sensitive means including first and second terminals movable relative to each other in response to variations in pressure, said first and second terminals being coupled respectively to said first and second auxiliary frame members, so that movement of said terminals relative to each other causes movement of said auxiliary frame members relative to each other; and means to indicate the position of rotation of the pivot frame member.

IRA E. McCABE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,599,466 Gourdou Sept. 14, 1926 1,983,305 Paulin Dec. 4, 1934 1,998,136 Jaenichen et a1. Apr. 16, 1935 2,149,216 Gravley Feb. 28, 1939 2,315,137 Shaw Mar. 30, 1943 2,377,182 Raspet May 29, 1945 2,454,647 Gille NOV. 23, 1948 FOREIGN PATENTS Number Country Date 1,185 Great Britain May 14, 1860 6,247 Great Britain Mar. 16, 1909 11,485 Great Britain June 2, 1899 364,748 Italy Nov. 12, 1933 495,550 France July 4, 1919 

